13.9×137/138+137×1又1/138=139*0.1*137/138+137*139/138=139*137*(0.1+1)/138=209473/1380
(11/19×0.317+0.317×18/19-0.317)÷3.17-(0.875-3/4+1/8-0.25)=0.317*(11/19+18/19-1)/3.17-(7/8-6/8+1/8-2/8)=0.1*(11+18-19)/19-(7-6+1-2)/8=1/19-0=1/19